Field of Disclosure
The following relates generally to wireless communication, and more specifically to quality of service (QoS) related enhancements for Long Term Evolution (LTE) operation over shared spectrum.
Description of Related Art
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, single-carrier frequency-division multiple access (SC-FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a first wireless multiple-access communication system may operate according to a radio access technology (RAT), such as LTE, and may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station). A second wireless multiple-access communications system may operate according to a different RAT, such as Wi-Fi, and may include a number of base stations or access points (APs), each simultaneously supporting communication for multiple mobile devices or stations (STAs). APs may communicate with STAs on downstream and upstream links. In some cases both types of communication systems may operate in the presence of one another and may use shared resources.
In a wireless local area network (WLAN), such as Wi-Fi, an AP may communicate with multiple STAs over a shared radio frequency spectrum. The STAs may use contention procedures such as listen before talk (LBT) that include a clear channel assessment (CCA) procedure to determine whether a channel of the shared radio frequency spectrum is available. The contention procedures may also involve communicating one or more control frames prior to establishing a communication link, such that confirmation of the communication link via exchange of control frames limits interference experienced by nearby communication devices. One example of such techniques include Request to Send (RTS) and Clear to Send (CTS) messaging, where, for example, a STA looking to communicate with another device (e.g., another STA or AP), may first send an RTS frame to the device. Once the recipient device receives the RTS frame, the recipient device may confirm the communication link by sending a CTS frame. After the CTS frame is received by the STA, the STA may then begin transmitting data to the recipient device. In this way, RTS/CTS messaging can reduce frame collisions by enabling a device, such as a STA or AP, to in essence clear the communication path before transmitting data to an AP or STA.
In an LTE network, a base station may communicate with UEs over carriers in a dedicated frequency spectrum (e.g., operator-licensed frequency band) using a multiple access technique where resources of the carrier are centrally allocated by the base station. With increasing data traffic in cellular networks that use a dedicated (e.g., licensed) radio frequency band, offloading of at least some data traffic to a shared (e.g., unlicensed) radio frequency spectrum may provide a cellular operator with opportunities for enhanced data transmission capacity. A shared radio frequency spectrum may also provide service in areas where access to a dedicated radio frequency spectrum is unavailable. An LTE device that is capable of operating in shared frequency spectrum using LTE-based transmission protocols may be considered to be an LTE-Unlicensed (LTE-U) device.
Prior to gaining access to and communicating over a shared radio frequency spectrum, an LTE-U base station or UE may perform an LBT procedure compatible with contention procedures used by Wi-Fi devices to gain access to the shared radio frequency spectrum. Thus, LTE-U and Wi-Fi devices contending for access to the same shared radio frequency spectrum may each be able to transmit and receive communications while mitigating interference from other users.
In some cases, a network employing LTE-U operation may have multiple base stations within a geographic area that may be deployed in various configurations. For example, based on their separation distance, transmissions from one base station over a carrier of a shared spectrum may or may not cause a neighboring base station to detect the carrier as busy. Additionally, a network operator can tune transmission power to mitigate interference between neighboring base stations. However, the network deployment may not take into account other users of the shared spectrum and challenges may occur in managing interference between base stations employing LTE-U operation and other users.